Re: [PATCH 5/5] blkcg: remove blkio_group->stats_lock

[Vivek Goyal]

On Thu, Mar 08, 2012 at 10:54:00AM -0800, Tejun Heo wrote:
> With recent plug merge updates, all non-percpu stat updates happen
> under queue_lock making stats_lock unnecessary to synchronize stat
> updates.  The only synchronization necessary is stat reading, which
> can be done using u64_stats_sync instead.
> 
> This patch removes blkio_group->stats_lock and adds
> blkio_group_stats->syncp for reader synchronization.
> 

Good to see stat_lock going away. That lock was confusing as we were doing
updates under queue_lock anyway. One less lock to think about now.

This stat code is messy though. All time related stat, maintaining flags,
dividing stats between read/write, sync/async. I think we are maintaining
way too much of stat. (/me wished there was a way to get rid of some of
the stats and make code simpler).

Thanks
Vivek
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